1. Field of the Invention
The present invention relates to a touch panel used for an operation of various electronic devices.
2. Background Art
In recent years, various electronic devices such as a mobile phone and a car navigation system include very sophisticated and diversified functions and have began to increasingly incorporate therein an optically-transparent touch panel attached to a front face of a display element (e.g., liquid crystal). A user of such an electronic device depresses and operates the touch panel by a finger or a pen while visually recognizing, through the touch panel, the display on the display element at the back face of the touch panel. Through this operation, the respective functions of the electronic device are switched. Thus, a touch panel having a superior visibility and providing secure operation and an electric connection is required.
A conventional touch panel will be described with reference to FIG. 7 to FIG. 9.
FIG. 7 is a plane sectional view illustrating a conventional touch panel. FIG. 8 is a front sectional view taken along a line 8-8 of the touch panel shown in FIG. 7. In FIG. 7 and FIG. 8, upper substrate 101 has a film-like shape and is optically-transparent. Upper substrate 101 has, at a lower part thereof, optically-transparent lower substrate 102. At a lower side of upper substrate 101, optically-transparent upper conductive layer 103 is formed by material such as indium tin oxide. At an upper side of lower substrate 102, lower conductive layer 104 is similarly formed by material such as indium tin oxide.
Both ends of upper conductive layer 103 have a pair of upper electrodes (not shown). Both ends of lower conductive layer 104 have lower electrodes 105 formed in a direction orthogonal to the upper electrodes. The upper electrodes and lower electrodes 105 extend along an outer periphery of upper conductive layer 103 and lower conductive layer 104. Ends of upper substrate 101 and lower substrate 102 have a plurality of lead sections including lead sections 105a, 105b. Specifically, lead section 105a and lead section 105b are lead sections of lower electrode 105. It is noted that the upper electrode and lower electrode 105 are made of a conductive material (e.g., silver).
Slit 106 is provided at the inner side of lower electrode 105. Slit 106 is obtained by removing lower conductive layer 104 by a laser cut or an etching processing and others. A slit (not shown) is provided between the upper electrodes. The slit is similarly obtained by removing upper conductive layer 103 by a laser cut or an etching processing and others. Insulating groove 106a connected to slit 106 is provided between lead section 105a and lead section 105b, for example. The structure as described above prevents a short circuit between lead section 105a and lead section 105b. 
At an upper surface of lower conductive layer 104, a plurality of dot spacers (not shown) made of insulating resin are formed with a predetermined interval therebetween. Spacer 107 having a substantially frame-like shape is provided at an outer periphery of a lower face of upper substrate 101 or an outer periphery of an upper face of lower substrate 102. An upper face and a lower face of spacer 107 are coated with adhesion layers (not shown). As a result, an outer periphery of upper substrate 101 is adhered with an outer periphery of lower substrate 102, and upper conductive layer 103 is facing to lower conductive layer 104 with a predetermined space therebetween. In this manner, touch panel 100 is provided.
Touch panel 100, thus structured, is placed on a front face of a liquid crystal display element (not shown) and others, and is attached to an electronic device. A plurality of the lead sections provided at the end section of the upper electrode and the end section of lower electrode 105, for example lead sections 105a, 105b, are connected to an electronic circuit of an electronic device (not shown), via a wiring substrate (not shown), in which an upper face and a lower face have a plurality of wiring patterns.
In the structure as described above, an upper face of upper substrate 101 is depressed and operated by a finger or a pen while the display of a liquid crystal display element provided at the back face of touch panel 100 being visually recognized. As a result, upper substrate 101 is bent and upper conductive layer 103 at the depressed portion is come into contact with lower conductive layer 104.
Then, a voltage is sequentially applied from the electronic circuit, via the wiring substrate, to the upper electrode and lower electrode 105. The applied voltage is sequentially applied to both ends of upper conductive layer 103 and both ends of lower conductive layer 104 in a direction orthogonal to upper conductive layer 103. Based on a voltage ratio of the upper electrode and a voltage ratio of lower electrode 105, the depressed position is detected by the electronic circuit. As a result, various functions of the electronic device are switched.
Since conventional touch panel 100, as described above, has been increasingly mounted in a device having a smaller size and a more sophisticated function, an interval between a plurality of lead sections connected to a wiring substrate has been required to be smaller. For example the interval between lead section 105a and lead section 105b has been required to be smaller. Specifically, a pitch therebetween has been required to be smaller. However, touch panel 100 is generally structured so that upper conductive layer 103 and lower conductive layer 104 are removed by laser cut or an etching processing to form the slits and the insulating grooves including slit 106 and insulating groove 106a. Thereafter, electrodes including the upper electrode, lower electrode 105, and lead sections 105a, 105b are formed at the outer periphery of upper conductive layer 103 and an outer periphery of lower conductive layer 104 by a printing technique or the like.
Specifically, the formation of insulating groove 106a and the formation of electrodes including the upper electrode and lower electrode 105 are generally separately performed. Thus, insulating groove 106a formed between lead sections 105a, 105b is positioned in a dislocated manner due to a tool change operation between the formation of insulating groove 106a and the formation of the electrodes or a machining apparatus positioned in a dislocated manner and others.
This causes, as shown in FIG. 9, an increased dislocation between lead sections 105a, 105b and insulating groove 106a. As a result, insulating groove 106a is dislocated to further left from lead section 105a for example, thus failing to provide insulating groove 106a in lower conductive layer 104 between left lead section 105a and right lead section 105b. Consequently, a space between lead section 105a and lead section 105b is short-circuited by lower conductive layer 104.
It is difficult to reduce a pitch between lead sections 105a, 105b in order to prevent the short-circuiting between lead section 105a and lead section 105b. Thus, a gap of about 1.2 mm is generally provided between lead section 105a and lead section 105b, and insulating groove 106a is provided in the vicinity of the center of between lead section 105a and lead section 105b. This suppresses, even when lead sections 105a, 105b or insulating groove 106a are/is provided with some dislocation, the short circuit between lead section 105a and lead section 105b to maintain insulation.
Conventional touch panel 100 as described above is disclosed, for example, in Japanese Patent Unexamined Publication No. 2003-58319.